The problems posed by substances which deplete the atmospheric ozone layer (ODP: ozone depletion potential) were tackled at Montreal, where the protocol imposing a reduction in the production and use of chlorofluorocarbons (CFCs) was signed. This protocol has been the subject of amendments which have required that CFCs be withdrawn and have extended regulatory control to other products.
The refrigeration industry and the air conditioning industry have invested a great deal in the replacement of these refrigerant fluids.
In the automotive industry, the air conditioning systems for vehicles sold in many countries have changed from a chlorofluorocarbon (CFC-12) refrigerant fluid to a hydrofluorocarbon (1,1,1,2-tetrafluoroethane: HFC-134a) refrigerant fluid which is less harmful to the ozone layer. However, from the viewpoint of the objectives set by the Kyoto protocol, HFC-134a (GWP=1300) is regarded as having a high warming potential. The contribution to the greenhouse effect of a fluid is quantified by a criterion, the GWP (Global Warming Potential), which indexes the warming potential by taking a reference value of 1 for carbon dioxide.
In the field of heat pumps, substitutes for dichlorotetrafluoroethane (HCFC-114), used under conditions of high condensing temperature, have been proposed. Thus, document U.S. Pat. No. 6,814,884 describes a composition comprising 1,1,1,3,3-pentafluorobutane (HFC-365mfc) and at least one compound chosen from 1,1,12-tetrafluoroethane, pentafluoroethane (HFC-125), 1,1,1,3,3-pentafluoropropane (HFC-245fa) and 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea). However, these compositions do not have a very high performance since they have a large temperature glide and a low heat capacity (the heat capacity is less than 60% compared to HCFC-114); moreover, the presence of HFC-227ea and HFC-125 leads to a high GWP.
Document U.S. Pat. No. 5,788,886 discloses compositions of pentafluoropropane and a fluoropropane such as tetrafluoropropane, trifluoropropane, difluoropropane or fluoropropane; 1,1,1,4,4,4-hexafluorobutane; (CF3)2CHCH3; 1,1,1,2,3,4,4,5,5,5-decafluoropentane; a hydrocarbon such as butane, cyclopropane, isobutane, propane, pentane; or propylene; or dimethyl ether. This document teaches the use of these compositions especially as refrigerants, cleaning agents and blowing agents.
Binary azeotropic or azeotrope-like mixtures are also disclosed in this document. Mention may especially be made of the binary mixture of 1,1,1,3,3-pentafluoropropane and pentane.
Document U.S. Pat. No. 5,672,294 discloses azeotropic or azeotrope-like compositions of 1,1,1,3,3-pentafluoropropane and at least one hydrocarbon chosen from n-pentane, isopentane, cyclopentane, n-hexane and isohexane. It teaches the use of these compositions as blowing agents in the manufacture of polyurethane and polyisocyanurate foams, and also as an aerosol propellant.